<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<canvas id="test" style="background: #000000;"></canvas>
	</body>
</html>
<script>
	var canvas = document.getElementById('test');
	var ctx = canvas.getContext('2d');
	canvas.width = window.innerWidth;
	canvas.height = window.innerHeight;
	var ball = new Ball();
	
	
	var Ball = funciton(){
		ctx.save();
		ctx.fillStyle = "red";
		ctx.arc(canvas.width/2, canvas.height/2, 20, 0, Math.PI*2)
		ctx.restore();
	}
	
</script>